.banner { position: relative; overflow: auto; }
.banner li { list-style: none; }
.banner ul li { float: left; }
.banner .dots {
    position: absolute;
    left: 0;
    right: 0;
    bottom: 20px;
    text-align: center;
}
.banner .dots li {
    display: inline-block;
    width: 10px;
    height: 10px;
    margin: 0 4px;
    text-indent: -999em;
    border: 2px solid #fff;
    border-radius: 6px;
    cursor: pointer;
    opacity: .4;
    transition: background .5s,opacity .5s;
}
.banner .dots li.active {
    background: #fff;
    opacity: 1;
}